Abstract: A method, apparatus, system, and signal-bearing medium that in an embodiment determine, after a restore of a version of an object, where to begin applying changes from a change log to the object based on an identification in the saved version of the object. When a save command for an object is received, an identification of the change log entry associated with the save command is stored in the saved version of the object. Changes to the object then continue to be logged to the change log. After the saved version of the object is restored, the identification in the saved version of the object is used to find the change log entry at which to start applying changes from the change log to the object. In this way, the point in the change log at which to start applying changes to the object may be determined based on the saved version of the object. In an embodiment, this allows the object to continue to be accessed while the save operation is performed.

Abstract: A flux indicator is utilized as a low-overhead consistency check for a shared resource such as a data structure, and provides a mechanism for determining both whether a data structure has or is currently in the process of being modified. In connection with attempts to modify the data structure, the flux indicator is updated from a first state to a second state prior to modifying the data structure, and thereafter updated to a third state after modifying the data structure, Copies of the flux indicator are then obtained both before and after attempting to obtain a copy of data from the data structure. The validity of the copy of the data is ensured when the first copy of the flux indicator does not indicate that the data structure is in the progress of being modified and the first and second copies of the flux indicator have the same state.

Abstract: An apparatus and method includes a database journal that records journal entries. Each journal entry includes a validation value that is computed from the data and metadata for the record before it is changed. In this manner, journal entries may be applied with confidence to a record in a database. This is especially useful when minimized data journal entries are used. If the validation value of the journal entry matches the validation value computed from the data and metadata of the record that the journal entry is to be applied to, then the record before applying the journal entry is identical to the record in the original database, and the journal data may be applied to the database record. If the validation value of the journal entry does not match the validation value computed from the data and metadata of the record that the journal entry is to be applied to, the record is not the same as in the original database when the journal entry was generated.

Abstract: A flux indicator is utilized as a low-overhead consistency check for a shared resource such as a data structure, and provides a mechanism for determining both whether a data structure has or is currently in the process of being modified. In connection with attempts to modify the data structure, the flux indicator is updated from a first state to a second state prior to modifying the data structure, and thereafter updated to a third state after modifying the data structure, Copies of the flux indicator are then obtained both before and after attempting to obtain a copy of data from the data structure. The validity of the copy of the data is ensured when the first copy of the flux indicator does not indicate that the data structure is in the progress of being modified and the first and second copies of the flux indicator have the same state.

Abstract: A protection utility for compiled data in a computer system having dynamically configurable logical partitions determines the time for rebuilding compiled data, and selectively stores data in a form not requiring rebuild to meet a pre-specified recovery time limit. If the configuration changes, the protection strategy is automatically migrated to adapt to the new configuration. Preferably, the compiled data is multiple database indexes, which are selectively logged to reduce recovery time. Logging is selectively discontinued or extended responsive to changes in partition configuration, allowing a gradual migration to the target recovery time using the new set of configured resources.

Abstract: An apparatus, program product and method manage a queue through the use of element-based journaling to record changes made to logical elements in a queue. In contrast to convention memory-based journaling, where any changes to the memory representing an element in a queue are journaled, only those operations that affect the logical ordering and/or placement of an element on a queue, or the logical contents of such an element, are journaled. Memory management operations such as pointer manipulation operations that modify pointers or other memory management data, but do not otherwise modify the actual elements in a queue or their relative ordering, need not be journaled. As a consequence, the storage and processing overhead associated with journaling may be substantially reduced, thereby substantially reducing the overhead associated with maintenance and recovery of a queue.

Abstract: An apparatus and method includes a database journal that records journal entries. Each journal entry includes a validation value that is computed from the data and metadata for the record before it is changed. In this manner, journal entries may be applied with confidence to a record in a database. This is especially useful when minimized data journal entries are used. If the validation value of the journal entry matches the validation value computed from the data and metadata of the record that the journal entry is to be applied to, then the record before applying the journal entry is identical to the record in the original database, and the journal data may be applied to the database record. If the validation value of the journal entry does not match the validation value computed from the data and metadata of the record that the journal entry is to be applied to, the record is not the same as in the original database when the journal entry was generated.

Abstract: A protection utility for compiled data in a computer system having dynamically configurable logical partitions determines the time for rebuilding compiled data, and selectively stores data in a form not requiring rebuild to meet a pre-specified recovery time limit. If the configuration changes, the protection strategy is automatically migrated to adapt to the new configuration. Preferably, the compiled data is multiple database indexes, which are selectively logged to reduce recovery time. Logging is selectively discontinued or extended responsive to changes in partition configuration, allowing a gradual migration to the target recovery time using the new set of configured resources.